Sildenafil is a representative therapeutic agent among various commercially available agents for treating erectile dysfunction, and it has been commercially available in the form of a tablet formulation containing sildenafil citrate.
When having to use therapeutic agents for erectile dysfunction, in terms of transportability, it is preferable to use film forms, which are often called strips.
However, sildenafil citrate is commercially available in 25, 50 or 100 mg sildenafil citrate-containing tablets, but due to a high single dose, it is not feasible to formulate in a film form. Specifically, the total weight of commercially available film formulations is mostly in the range of 30 to 100 mg, and an active ingredient containing a high dose is difficult to formulate in a film form for the following reasons:
First, in the preparation of a film formulation, a fixed amount of polymer or more must essentially be used to maintain the form of a film. However, in order to load a high amount of an effective ingredient in a limited film size, the amount of such a polymer can only reduce. In the case the amount of polymer is not sufficient, the formed film may not have the desired properties (e.g., flexibility and tension) for handling.
Second, to contain a high amount of active ingredient in a film, the inherent properties of an active ingredient must be overcome. However, if the amount of additives is restricted, it is difficult to offset the inherent properties. Furthermore, if an active ingredient is not dissolved but just dispersed or suspended in the film-making solution, the layer separation of the film-making solution or the non-homogenization of the active ingredient may occur. Such a layer separation or non-homogenization may also occur during preparation of the film-making solution, transportation of the solution for coating, and coating and drying processes.
Third, it is general to increase the viscosity of a solution or suspension for forming a film in the preparation of a film containing a dispersed or suspended active ingredient in a high amount. However, an excessive viscosity may adversely affect the characteristics and quality of a dried film. Accordingly, high viscosity may be a drawback in terms of good production.